Charging motorhome batteries with a solar trickle charger

i was going to use just a simple 110vcoil 30A relay across the mains coming in, the two normally open contacts connect the two positive terminals together of the batterys. I know when the engine is running it will charge both batterys as well.

77rollalong wrote:
i had the chassis battery in ours go dead a couple of weeks ago, while the house battery was fine. as an interm i have jumpered the two together, and put a solar charger on the chassis battery, and left the rv plugged in to keep them both charged. been thinking of putting in another relay to connect both batterys together only when its plugged into 110v shore power

Winnebagos(at least many or even most) have that set up but the solenoid that connects to two batteries, house and chassis is activated by ignition switch. This allows both sets of batteries to be charged by the engine alternator. It is also activated by the Boost Switch on the dash. If you by an Intelitec latching relay like the one Winnie uses, and activate/deactivate it using a SP/DT Momentary switch with a center off position, you can activate and connect both batteries for charging by the converter or deactivate and have them charge normally while the engine is running.

There are probably hundreds of latching relays that would work but I am familiar with the Intelitec relay. By using a latching relay, there is no drain to hold the relay closed.

If I have confused you about the latching relays, ask DougRainer or Chris Bryant to help. That's where I learned about how Winnies are wired, them and the full set of diagrams from Winnebagoind.com.

i had the chassis battery in ours go dead a couple of weeks ago, while the house battery was fine. as an interm i have jumpered the two together, and put a solar charger on the chassis battery, and left the rv plugged in to keep them both charged. been thinking of putting in another relay to connect both batterys together only when its plugged into 110v shore power

I just hooked my Deltran Solar Trickle Charger to the house batteries with cable clamps. When I run the generator every month, I take the rig for a little run. Not long or far but just to circulate all the fluids and move all the rotating parts and that keeps the chassis battery charged.

You could buy a latching relay and wire it in parallel to the chassis battery.

My battery disconnect is a latching relay that is operated by a single pole double momentary throw switch. Kind of expensive but it would work.

Easier to run the engine at the same time you exercise the generator.

By the way, this is on the back of my rig.

Disconnect the house batteries. Check voltage once a month and charge if voltage is below 12.5, using the converter (reconnect), regular charger or trickle charger (for a much longer time).

Thanks everyone for the ideas. We are thinking of cutting a hole in the cover as the easiest solution. Until then, just running the engine for a while to charge everything.

Typically on the Ford E series chassis, the cigarette lighter socket is live all the time (with the key off), so there's no special wiring to do to use one of those little solar maintainers. This is pretty easy to check with any sort of a lighter accessory; if it works with the key off/out, the charger will also work.

When we bought our RV new to us, they gave a solar charger and the cigarette plug was somehow rigged to allow power to go back into the chassis battery. When we had an electrical problem and took it to the Ford dealer, they removed all the wiring and fuses that were jumped together explaining that that was the cause. After that I haven't used the solar charger, but if this is a common practice and the cigarette lighter does successfully charge the battery then I would love to you. Sorry to piggyback on this question but I didn't realize this may be common practice and thought it was a one-off that the previous owner had done.

I’m assuming that you do not have access to “shore power”, If that is the case.... I think that I would get a “second” solar charger and connect directly to the coach batteries.

No. Enabling the coach batteries won't help by itself, because the 12V cigarette outlet your trickle charger is plugged into only connects to the chassis battery, as you mentioned it was charging it.
If there are any other 12V cigarette lighter outlets back in the coach that you know run off the coach batteries, then enable the battery disconnect, and plug a second trickle charger into one of them. That should charge the coach batteries, if they aren't too far gone.

Or, you could plug your shore power cord into 120VAC and use the converter charger to charge the house batteries, but if your circa 2000 unit has the original converter/charger, it probably isn't a smart charger, and would probably overcharge your coach batteries. Do you know if your converter/charger was ever upgraded with a smart (3 way) charger?

Or as Drew suggested, pull the cover off. Or cut a hole in it big enough to let some sun hit the panel.